I am sorry your DS is having such a hard time w/ this DD. I don't know if more young ppl are getting this lately, or if it finally being recognized while ppl are younger. I've had this all my life, it has gotten worse thru the yrs, but I've always had it.
When I finally had an idea that there was 'something specifically wrong' w/ me, I tried to get my pcp to hear me. She was not very receptive. She felt I was a malingerer. I put myself thru college, worked FT, got married, raised 3 children, again worked FT as a teacher, took my children for ALL their activities, taught a religious program at my church, took my DM to all of her dr appt, shopping, her church activities and did the baking for her meetings, then housework, cooking and baking for my own family. It got to the point where I was struggling to do what I had always done. The dr thought I was lazy. Lazy, no!, exhausted, YES!
I had to give up the career I trained for and LOVED! It is a blow to the ego, self-esteem, ect. I try to do the things I need to do, and I push myself to do these things. I can't do all the things I want to do, things I used to do, but I am busy doing what I can do.
I was happy - strange as that sounds - when I got the official dx of Fibro. I was afraid other things were wrong that would have taken my life. I have other conditions that add to my fun, but I will survive.
I wish your DS would join us here, it may help him to accept this and start to move on w/ his life. When you realize others understand just what you mean, it helps so much.
I know it hurts to see your child hurting, physically and emotionally. That is the hardest part of being a parent. I will keep both of you in my prayers.
God bless. Alice.